Wireless device transmissions often are subject to governmental regulations (e.g., United States Federal Communications Commission (FCC) regulations) regarding the spectral content of transmitted waveforms. In order to filter outgoing signals so that they are in compliance with such regulations, some wireless transceivers include one or more surface acoustic wave (SAW) filters in the radio frequency (RF) portion of their transmitter subsystem. A SAW filter is an electromechanical device that may function in the analog RF domain as a finite impulse response filter. Accordingly, a SAW filter may be used to filter out various out-of-band noise components and spectral images.
Although SAW filters may perform adequately in many circumstances, the component cost of a SAW filter is non-negligible. This cost is multiplied for multi-band wireless transmitters and transceivers, which may include a SAW filter for each supported frequency band. Accordingly, what are needed are relatively low cost apparatus and methods for filtering a signal so that its associated transmitted waveform may comply with regulations regarding spectral content.